Posted: 11/05/2015 at 11:07
If you don't want to use chemicals, black plastic, or cardboard, can you devote enough time to keep going back to the allotment to weed it by hand AND keep on top of it?
What are your long term goals for this allotment? Have work / other commitments become any less demanding on your time that you can honestly say you'll be able to give yourself all the energy and efforts you need?
Or do you find someone to share the allotment with you? I'm sure the council will know if there's a waiting list of people who might be interested in a half plot.
I'm just thinking (since I know how quickly weeds take hold) that perhaps you might be better off using the black plastic and cardboard to TRY and suppress the areas you aren't working on straight away and break the plot into small patches to complete at a time.